Cutting ECU Power?

Would it be possible to wire an interrupt to the switched ECU power? I *think* that on my 1993 Nissan 240sx that there's two wires for ECU power. One while the car is off and one when the car is on. But anyway, is this at all feasible?

Sure it is feasible and possible, a relay or a switch could easily interupt any wire, but why on earth I ask do you want to do this?

Theft deterrent. I know that there's fuel pump, ignition & starter. I want to add ECU power to the list. Any other opinions?

P.S. Is anyone out there familiar with a 240sx ECU?

I am not familar with that ecu but perhaps you can locate a factory manual for the vehicle. Not like a haynes at the auto parts store but a factory one will tell you what every wire does by its color code. However, I don't reccomend you mess with the ecu, especially for what you want to do, too risky. If you want to interupt circuits go to the component power source and interupt there with a relay wired N/O. You can catch the fuel pump power feed behind the factory fuse, interupt ignition under the hood, all kinds of creative ways that don't require messing with the ecu or having to buy a real expensive factory manual. If your're really hard dead set on doing it you might have luck in the reference section at your local library. some have all kinds of factory manuals and although you can't check them out you can copy them there. Might even be on computors there now for all I know, its been a while, Hope I helped a little.

I've got a FSM, but the pinout is extremely hard to read. :(

I can imagine. The last time I used one was for when I was restoring a 1964 chevelle. Had to properly fix all the years of  electrical rigging in that poor car. As so primitive and basic compared to your car (no ecu's or anything really) it still took alot of concentration and the manual was so old that some things were unreadable. I wish you luck with the project but still feel you can add very effective layers of security without touching the ecu.

Most ECU's are computers that learn over time, killing power to would mean it will re-learn every time you activate the kill. Doesn't sound like a good idea to me....Mike M2

Tech Manager

CS Dealer Services

Well, that's what i'm asking. I thought there were two ECU power leads, one for constant power (to retain learned settings) and one for everything else when the car is on (distributor, tach signal, various sensors, etc). Suppose I interrupt the switched power wire (the one that controls everything when the car is on) with a killswitch. The car wouldn't start if the switch isn't tripped..

Hmmm, what if cranking the car with this power disconnected damages the ECU? It could be a possibility....Mike M2

Tech Manager

CS Dealer Services